Digital Video Broadcasting-Satellite-Second Generation (DVB-S2) is a standard for satellite broadcasting. In accordance with the DVB-S2 standard, a frame of data packed is known as a baseband frame (BBFRAME). BBFRAMEs can have variable lengths from 3072 to 58192 bits. Further, each frame when transmitted can have different Modulation and Coding rates, or MODCODs. Modulation defines the mapping of bits to symbols and hence defines the number of bits conveyed by a symbol, and coding is used for error correction.
The transmission of transport streams of BBFRAMEs from a transmitter to a receiver may be constant bit rate (“CBR”) or variable bit rate (“VBR”). DVB-S2 further supports an adaptive transmission mode: Adaptive Coding and Modulation (ACM). ACM adjusts the carrier's coding and modulation during transmission to optimize quality of service and throughput, adapting to changing link conditions. Thus, based on transmission conditions, a constant symbol rate can convey different bit rates of information.
A network transmitter device may be connected to a single outbound link. If the transmitter device supports multiple inbound client flows, the transmitter device is responsible for arbitrating the sharing of the single outbound link among the multiple inbound client flows.
One prior art arbitration scheme is a first-come-first-serve scheme. In this solution, packets are received by the transmitter device from inbound clients. The packets are transmitted by the transmitter device to the outbound link in the same order in which the packets are received. This scheme does not preclude one client from monopolizing or unfairly consuming the entire outbound link
Another prior art arbitration scheme is packet-wise round-robin. In this solution, the transmitter device periodically services each inbound client or incoming queue. The transmitter device sends a packet onto the outbound link each time an inbound client is serviced. This solution prevents a single flow from monopolizing the entire link. However, transmission is not a function of varying incoming packet sizes, and thus fairness among the inbound client streams cannot be guaranteed. Another variation of this scheme is to evaluate each incoming bit from the inbound client. However, while it provides the finest level of granularity, this approach consumes significant resources and is difficult to implement in practice.
None of the prior art methods, however, take into account the flexibility of varying the outbound modulation link encoding when scheduling packets for transmission. Thus, there is a need for systems and methods which take into account the adaptive modulation capability when transmitting frames to more efficiently schedule the multiplexing of input streams.